The construction of residential and commercial structures as well as the development of usable space has led to the use a variety of devices to overcome the natural contour of the land. Often times the most desirable locations in which to build a dwelling or other structure are those which have the most severe landscape. Wooded ravines, sloping hillsides, and cliffs which overlook rivers, lakes, and the like are all examples of naturally occurring landscapes which must often be overcome prior to the construction of a structure. In addition to the construction of buildings, the development of usable land in yards, playgrounds, lots, etc. also often requires the artificial contouring of the landscape.
While many structural elements have been used to artificially contour or define the landscape, retaining walls have been developed as a common means of supporting, holding back, or otherwise altering the condition of the landscape. Generally, a retaining wall is a physical structure which rises above the plane of the landscape on one side of the wall to meet an adjacent but more highly positioned soil on the opposite side of the wall.
Retaining walls may be formed from any number of materials including steel or other metal alloys, wood, or block among other material. One material which has received wide and popular acceptance for use in the construction of retaining walls and the like is molded masonry blocks. Blocks used for these purposes include those disclosed by Risi et al, U.S. Pat. Nos. 4,490,075 and Des. 280,024 and Forsberg, 4,802,320 and Des. 296,007 among others. Blocks have also been patterned and weighted so that they may be used to construct a wall which will stabilize the landscape by the shear weight of the blocks. These systems are often designed to "setback" at an angle to counter the pressure of the soil behind the wall. Setback is generally considered the distance in which one course of a wall extends beyond the front of the next highest course of the same wall. Given blocks of the same proportion, setback may also be regarded as the distance which the back surface of a higher course of blocks extends backwards in relation to the back surface of the lower wall courses. In vertical structures such as retaining walls, stability is dependent upon the setback between structures courses and the weight of the blocks.
For example, Schmitt, U.S. Pat. No. 2,313,363 discloses a retaining wall bleek having a tongue or lip which secures the block in place and provides a certain amount of setback from one course to the next. The thickness of the Schmitt tongue or lip at the plane of the lower surface of the block determines the setback of the blocks. However, smaller blocks for use in residential applications and the like have to be made with smaller tongues or flanges in order to avoid compromising the structural integrity of the wall with excessive setback. However, manufacturing smaller blocks having smaller tongues using conventional techniques does not result in a block tongue or lip having adequate structural integrity. Concurrently, reducing the size of the tongue or flange may weaken and compromise this element of the block, the course, or even the entire wall.
Other problems often occur which prevents the production of blocks having a simple design capable of being used in both residential and commercial markets. For instance, blocks may be made individually but this is generally far too expensive for most applications. More commonly, composite masonry blocks are generally formed by block machines upside down, i.e. on their back. The compressive forces applied to the wet fill during casting in combination with the moisture present between compression head and the fill often prevents the clean definition of interlocking elements having a small enough proportion to provide minimal setback between the layers or courses of the wall. In turn, excessive setback compromises the stability of the structure and prevents the simple construction of walls without ancillary support systems.
One means of achieving minimal setback is by pinning or staking the blocks of a higher course to the previously placed blocks of a lower course as shown in Forsberg. However, the use of pin systems is often complex requiring the close supervision of laborers. Such an investment in time and manpower is often not supportable given the costs at which landscaping services are sold. Moreover, the omission or misplacement of pins from the blocks can compromise the structural integrity of the entire wall.
As can be seen the present state of the art of forming masonry blocks as well as the design and use of these blocks to build structure has definite shortcomings.